Health Literacy and Numeracy: Workshop Summary by Melissa G. French

Author:Melissa G. French
Language: eng
Format: epub
Tags: ebook, book
Publisher: The National Academies Press
Published: 2014-07-24T00:00:00+00:00

WHY ARE YOU GIVING ME THIS NUMBER?: COMMUNICATING QUANTITATIVE INFORMATION FOR DECISION MAKING

Brian J. Zikmund-Fisher, Ph.D.

Department of Health Behavior and Health Education,

University of Michigan

Zikmund-Fisher said his presentation was not a review of the evidence on numeracy, but an argument that he hoped would be provocative. He began with the example of a fictional person called “Robert” (Zikmund-Fisher, 2013a). Robert is a stereotypical middle-age man living in the United States. He is not as healthy as he should be or wishes to be because he has hypertension, is overweight, and does not get enough exercise. Robert decides to use an online risk calculator to find out whether he is at risk for cardiovascular disease. The risk calculator asks Robert his blood pressure, his weight and height, his cholesterol, and a few other pieces of information before providing the result. Robert learns that his 10-year risk of cardiovascular disease is 14.52 percent. But Robert is confused; he still does not know whether he is at high risk or not.

The number provided to Robert—14.52 percent—may be the best estimate of his risk of disease that modern medicine could give him, Zikmund-Fisher said. Yet that number does not meet Robert’s need for information. Robert’s risk is not being effectively communicated to him through that number. Zikmund-Fisher said there are several problems with the way that his risk of cardiovascular disease was communicated to Robert. First, there is the level of precision. Although it is common for risk calculators to give numeric risk estimates to two decimal points, it is not necessary or beneficial. Research has shown that an integer is considered more believable as well as easier to remember than a more precise representation of risk (Witteman et al., 2011).

More important, Zikmund-Fisher added, is the fact that Robert did not get the information that he needed from the number. Robert needed to know whether he was at high risk of developing cardiovascular disease or not. Merely giving him a number does not answer that question for him. Decision-making research uses the term “information evaluability” (Hsee, 1996), which means that the meaning of a number depends on its context and whether the number can be evaluated by itself or requires reference standards to convey meaning.

For example, Zikmund-Fisher said, if workshop participants were shown a number that corresponds to the level of dioxin in blood, many would not know how to evaluate that data (i.e., to know whether it represents a high or low concentration or even whether being high or low is good or bad). The sense of confusion that workshop participants likely felt when presented with information about dioxin is the same feeling that many patients have when they are given any type of number in a health or medical situation without the contextual knowledge to explain whether the number is good or bad. Another example might be a person with type 2 diabetes who is working to improve glycemic control. If this person starts with a hemoglobin A1c measurement of 9.3 percent and after some time lowers that number to 8.

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